Many arrangements exist in the prior art for cleaning moving webs such as paper webs. Dust and other entrained particles are often carried along by such webs and can present health and safety problems as well as quality control problems.
It will be appreciated that dust and other particles must be quickly and positively removed from fast moving webs such as those found in paper making and paper conversion facilities. The arrangement of the present invention accomplishes this objective in a highly efficient, relatively low cost manner. One of the components of the present system is a Coanda nozzle of specialized construction which is positioned relative to the web in a particular manner which provides a highly turbulent interface between air flow from the nozzle and the entrained layer of air moving with and bordered by the moving web.
While it is known generally to deploy one or more Coanda nozzles along the path of a moving web to treat the web in some manner or direct movement of the web, the arrangement of the present invention incorporates structure and method steps which cooperate in a unique manner to effectively and positively clean even very fast moving webs.
The following United States patents are believed representative of the current state of the art in this field: 4,932,140, issued Jun. 12, 1990, 4,594,748, issued Jun. 17, 1986, 3,650,043, issued Mar. 21, 1972, 3,629,952, issued Dec. 28, 1971, 3,587,177, issued Jun. 28, 1971, 2,515,223, issued Jul. 18, 1950, 3,078,496, issued Feb. 26, 1963, 3,775,806, issued Dec. 4, 1973, and 4,247,993, issued Feb. 3, 1981.
U.S. Pat. No. 3,775,806 discloses apparatus for removing and collecting dust from a traveling sheet or web of material including a blow box having means for impinging jets of clean air against the sheet both in the direction of travel of the sheet and in the opposed direction. A suction box cooperates with the blow box to form suction gaps withdrawing the air after its engagement with the material to remove the dust from the material.
U.S. Pat. No. 3,078,496 discloses web cleaning apparatus for cleaning a running web of material, such as paper, fabric, or plastic. A pressurized flow of air flows through a restricted passageway about a bulbous element and impinges against a moving web. The direction of web travel and the direction of the air flow are virtually identical. The air flow and entrained matter are then drawn into a suction box.
U.S. Pat. No. 4,932,140 discloses a nozzle box having a carrying face placed facing a web. Two nozzle slots blow toward each other with flow converging above the carrying face. The arrangement of this patent is intended for contact-free supporting and treatment, such as drying, heating or cooling, of paper webs and other continuous webs.
U.S. Pat. No 4,594,748, discloses an apparatus for cleaning particles from a web. An air flow is directed against the web through a pressure slit whereupon the air flow in deflected and guided along the web to two suction slits. The air flow is directed against the web by means of a nozzle in the shape of two expanding blades, each ending in an edge. The suction slits are surrounded by two blades and another two blades prevent the inlet of surrounding air.
U.S. Pat. No. 4,247,993 discloses nozzle apparatus for airborne paper web dryers of the non-impingement or under-pressure type including a blow box member defined by top web supporting and bottom wall portions and back and front wall portions. The front and top supporting wall portions are interconnected by a curved guide surface and an upwardly directed nozzle is provide on the front wall portion spaced below the entry edge plane of the guide surface.
U.S. Pat. No. 3,650,043 discloses an air foil web stabilizer constructed with its opposite ends disposed generally at a slight angle to provide a lateral component to the air discharge in the general direction of web movement to thereby remove wrinkles from the web.
U.S. Pat. No. 3,587,177 discloses an arrangement for the treatment of surfaces such as a web of material to be cleaned, dried or stabilized without physical contact with the web. An air foil nozzle is provided from which cleaning, drying or stabilizing gas is discharged tangentially against the web.
U.S. Pat. No. 3,629,952 discloses an air foil nozzle adjacent a moving web to be dried and constructed with a substantially flat planular guide surface trailing the nozzle, facing the web and substantially parallel thereto.